Percentage Calculator
Switch modes to answer everyday percentage questions — discounts, exam scores, price hikes, and growth rates — without memorizing formulas.
Inputs
Result
—
Percentage formulas (quick reference)
Part from percent: To find what P% of Y equals, compute Y × (P/100). That is the discount amount if Y is list price, or the tip if Y is the bill before tip — always confirm whether tax is included.
Ratio to percent: “X is what percent of Y?” answers (X / Y) × 100 when Y ≠ 0. Use it for conversion rates, test scores, or market share.
Increase/decrease by a percent: Increasing Y by P% yields Y × (1 + P/100); decreasing uses Y × (1 − P/100). Watch for compound successive changes — two 10% increases are not the same as one 20% increase.
Percent change between two values: From X to Y, use ((Y − X) / |X|) × 100. The result is positive if Y > X and negative if Y < X. If the starting value is zero, percent change is undefined — we surface an error instead of dividing by zero.
FAQ
Why is percent change undefined?
Starting from zero, relative change has no meaningful ratio — talk in absolute terms instead.
Do you round?
We show enough decimals for clarity; bank rounding rules may differ.
Can I use negatives?
Yes — for example, loss vs profit comparisons, as long as denominators stay valid.